1. Field of the Invention
The present invention relates to a transmission managing apparatus which, in an information transmitting system for using serial buses to connect a plurality of information processing apparatuses to each other and transmitting information mutually between the information processing apparatuses, manages the condition in the transmission of the information; the information processing apparatus included in the information transmitting system together with the transmission managing apparatus; and the information transmitting system including the transmission managing apparatus and the information processing apparatus.
2. Description of the Related Art
Recently, a so-called IEEE 1394 standard (a regular name is xe2x80x9cIEEE (Institute of Electrical and Electronic Engineers) Std. 1394-1995 IEEE Standard for a High Performance serial Busxe2x80x9d) is published as a new standard to transmit information in real time through serial bus Between a plurality of information processing apparatuses (for example, between a personal computer and a digital video camera or MD (Mini Disc) and the like). Accordingly, a digital video camera, a personal computer and the like having serial ports in accordance with the IEEE 1394 standard have been manufactured.
This IEEE 1394 standard standardizes that a plurality of information processors (hereafter, merely referred to as nodes) are connected to each other through serial buses to then transmit in time division the information corresponding to a plurality of channels between the respective channels (this standard standardizes that information can be transmitted by using a maximum of 63 different channels within a system connected through one serial bus).
Here, the IEEE 1394 standard standardizes the execution of an initialization of a serial bus referred to as a so-called xe2x80x9cbus resetxe2x80x9d, when another node is newly connected to node groups already connected to each other through the serial buses (namely, at a time of bus connection), or when one node is disconnected from the node groups (namely, at a time of bus open). Then, the following processes are executed in conjunction with the bus reset to accordingly establish a new connection condition (hereafter, the connection condition is referred to as a xe2x80x9ctopologyxe2x80x9d).
(1) In conjunction with an occurrence of a bus reset, a bus reset signal indicative of the occurrence of the bus reset is transmitted to all nodes in which a node detecting the occurrence of the bus reset (namely, a node to which another node is newly connected, or a node from which an existing connection is disconnected) is connected to a serial bus.
(2) Next, a tree identification to connect the respective nodes onto a tree is carried out after the bus reset. Then, a node located at a vertex of the connected tree is recognized as a route node.
(3) Next, the recognized route node makes each node recognize an identification number (ID number) peculiar to each node to identify each node within a tree system.
(4) Next, an IRM (Isochronous Resource Manager) node is set which is a node for managing the communication states (actually, channels used by the respective nodes and later-described transmission occupation periods) in all the nodes in the generated tree, and then displaying the current usage channels and the transmission occupation periods currently occupied by the respective nodes, in such a condition that can be identified by the other nodes.
(5) Finally, a bus manger is set which is a node for controlling the information transmission states of all the nodes.
A new topology after the bus reset is established through the above-mentioned process composed of five steps.
Then, in case that the information is actually transmitted after the establishment of the topology, a transmission node which is a node trying to start transmitting the information inquires of the IRM nodes the current communication states of the other nodes. If it is possible to use a channel and a transmission occupation period that the transmission node desires to use, the transmission node obtains a right of transmitting the information (actually, the transmission node insures the channel and the later-described transmission occupation period which the transmission node desires to use), and then starts the transmission of the information. At this time, immediately before the transmission of the information, the transmission node transmits to the IRM nodes a report of re-writing a display of a communication state in the IRM node (namely, since the start of the transmission of the information in the transmission node causes the transmission occupation period and the channel currently being used on the serial bus to be changed, it is necessary to re-write the displayed content into a new communication state after this change). The IRM nodes receiving this report respectively execute a process of updating the displayed content. After that, the content displayed after the update can be referred by the other nodes.
The transmission occupation period will be schematically described below.
In the IEEE 1394 standard, information from each node is transmitted as collection for each information unit referred to as an xe2x80x9cisochronous cyclexe2x80x9d (here, this xe2x80x9ccyclexe2x80x9d implies one cycle generated after division in time sharing on a serial bus). This isochronous cycle includes an isochronous transmission area and an asynchronous transmission area. The isochronous transmission area contains information transmitted synchronously with the information included in another isochronous cycle (e.g., video information or audio information). The asynchronous transmission area contains the information transmitted asynchronously with and independently of other information (e.g., control information to control an output of the video information or the audio information). Then, the information within this isochronous transmission area is divided in time sharing for each different channel, and different information is transmitted for each channel.
At this time, in the isochronous transmission area, it is standardized that a temporal length of the isochronous transmission area within one isochronous cycle is 100 xcexcsec at its maximum. Thus, it is necessary that a total period occupied by the information assigned to each channel within one isochronous transmission area for its transmission is also 100 xcexcsec or less. At this time, a transmission period within the isochronous cycle occupied by the one channel is the above-mentioned xe2x80x9ctransmission occupation periodxe2x80x9d.
In addition, this transmission occupation period may be referred to as a xe2x80x9cusage bandxe2x80x9d of a serial bus depending on a case, or it may be referred to as a xe2x80x9cusage capacityxe2x80x9d of a serial bus. On the other hand, if a length of the isochronous transmission area is less than 100 xcexcsec within the one isochronous cycle (including a case of zero), a period within an isochronous cycle other than the isochronous transmission area is used only as the asynchronous transmission area.
However, according to the IEEE 1394 standard having the above-mentioned configuration, when each transmission node starts transmitting the information, each transmission node needs to start the transmission after inquiring of the IRM node a communication state on the serial bus, checking whether or not a channel and a transmission occupation period which each transmission node desires to use can be actually used, and then insuring them if they can be used (in addition, those inquiring, checking and insuring operations are typically referred to as an xe2x80x9carbitration operationxe2x80x9d on the standard).
This necessity implies the following necessity, in other words. That is, if the channel and the transmission occupation period which the transmission node desires to use cannot be used, the transmission node transiently holds the start of the information transmission. After that, it again inquires of the IRM node the channel and the transmission occupation period, and starts the information transmission only after checking and confirming that the desired channel and transmission occupation period can be used.
At this time, if the channel and the transmission occupation period cannot be insured when the inquiry as to the IRM node is once carried out, the similarly referring and insuring operations are again repeated after a wait of a preset predetermined period. However, in this case, if the communication state on the serial bus is not updated in the predetermined period (the communication state on the serial bus (i.e., the channel currently being used and the transmission occupation period currently being occupied) is not always changed in the predetermined period), this results in a problem that the transmission node needs to repeat a useless and meaningless operation of insuring the channel and the transmission occupation period which can not be insured.
In view of the whole serial buses, this problem leads to a problem that it is necessary to transmit a control signal necessary for the useless insuring operation and the like by dividing a part of the asynchronous transmission area having an upper limit, and there may be a case in which other necessary control signals and the like can not be transmitted at this time.
On the other hand, from the viewpoints of the situations of the respective nodes, the above-mentioned problems lead to a problem that the repetition of the useless insuring operation increases the burdens on the signal processes in the respective nodes.
The present invention is proposed in view of the above mentioned problems. It is therefore an object of the present invention to provide: a transmission managing apparatus which can prevent the occurrence of the useless operation of insuring the channel and the transmission occupation period when each node starts transmitting information, and accordingly improve a usage efficiency of the serial bus as a whole information transmitting system, and further prevent an increase of a process burden in each node; a node included in the information transmitting system together with the transmission managing apparatus; and the information transmitting system including the transmission managing apparatus and the node.
The above object of the present invention can be achieved by a first transmission managing apparatus included in a first information transmitting system comprising (i) a communication bus such as a serial bus, (ii) an indicating device such as an IRM node, which has a transmission state memory such as a resource register for storing a channel used for an information transmission executed in a time division manner on the communication bus and a transmission occupation period occupied for the information transmission, for indicating the channel and the transmission occupation period and (iii) a first information processing apparatus such as a node for insuring a non-used channel, which is the channel that is not used, and a preservable period, which is the transmission occupation period, that can be occupied, while referring to a memory content of the transmission state memory, to thereby carry out the information transmission. The first transmission managing apparatus is provided with: (a) a monitoring device such as a comparator for monitoring whether or not the memory content is updated; and (b) a reporting device such as a command generator for reporting a fact of updating of the memory content through the communication bus to the first information processing apparatus when the memory content is updated.
According to the first transmission managing apparatus of the present invention, when the memory content of the transmission state memory is updated, this fact of updating is reported to the information processing apparatus through the communication bus. Thus, it is possible to prevent a useless referring operation from being repeated by the information processing apparatus while the memory content is not updated.
Therefore, it is possible to prevent the communication bus from being used for the useless referring operation, so that the usage efficiency can be improved as a whole of the information transmitting system. Further, it is possible to prevent the process load from being increased by the useless referring operation in the information processing apparatus.
In one aspect of the first transmission managing apparatus of the present invention, the first transmission managing apparatus is further provided with a referring device memory such as a resource register for storing an identification number to identify one first information processing apparatus, which cannot insure the non-used channel and the preservable period, among first information processing apparatuses each referring to the memory content at a time of the information transmission, the reporting device reporting the fact of updating of memory content to the one first information processing apparatus.
According to this aspect, the fact of updating of the memory content is reported only to the information processing apparatus which could not transmit the information since the non-used channel and the preservable period could not be insured. Thus, it is possible to manage the transmission of the information efficiently within the information transmitting system.
In another aspect of the first transmission managing apparatus of the present invention, the first transmission managing apparatus is further provided with a detecting device such as a comparator for detecting the non-used channel that is newly generated and the preservable period that can be newly occupied, in conjunction with updating of the memory content, wherein, when the memory content is updated, the reporting device reports the detected non-used channel and the detected preservable period to one first information processing apparatus which cannot insure the non-used channel and the preservable period.
According to this aspect, the non-used channel and the preservable period are reported at least to the information processing apparatus, which could not insure the non-used channel and the preservable period, when the memory content is updated. Thus, it is possible for the information processing apparatus, which could not transmit the information, to speedily insure the non-used channel and the preservable period to thereby start transmitting the information.
The above object of the present invention can be also achieved by a first information processing apparatus included in the above described first information transmitting system of the present invention together with the above described first transmission managing apparatus of the present invention. The first information processing apparatus is provided with: (a) an insuring device such as a transmission controller for insuring a non-used channel, which is the channel that is not used, and a preservable period, which is the transmission occupation period, that can be occupied, while referring to the memory content, when the information is to be transmitted, and for insuring again the non-used channel and the preservable period on the basis of reporting of the reporting device when the insuring device cannot insure the non-used channel and the preservable period; and (b) a transmitting device such as a packet transmitter for carrying out the information transmission by using the insured non-used channel and the insured preservable period.
According to the first information processing apparatus, in case that the non-used channel and the preservable period cannot be insured, it is possible to prevent the useless referring operation from being performed while the memory content of the transmission state memory is not updated.
Therefore, it is possible to prevent the process load from being increased by the useless referring operation in the information processing apparatus.
The above object of the present invention can be also achieved by a first information transmitting system provided with the above described first transmission managing apparatus of the present invention and a plurality of first information processing apparatuses each having the same construction as the above described first information processing apparatus of the present invention, wherein the information transmission is carried out between the first information processing apparatuses.
According to the first information transmitting system, it is possible to prevent the useless referring operation from being performed while the memory content of the transmission state memory is not updated, so that it is possible to perform the transmission of the information efficiently.
The above object of the present invention can be also achieved by a second transmission managing apparatus included in a second information transmitting system comprising (i) a communication bus such as a serial bus, (ii) an indicating device such as an IRM node, which has a transmission state memory such as a resource register for storing a channel used for an information transmission executed in a time division manner on the communication bus and a transmission occupation period occupied for the information transmission, for indicating the channel and the transmission occupation period and (iii) a second information processing apparatus such as a node for insuring a non-used channel, which is the channel that is not used, and a preservable period, which is the transmission occupation period, that can be occupied, to thereby carry out the information transmission. The second transmission managing apparatus is provided with: (a) a monitoring device such as a comparator for monitoring whether or not a memory content of the transmission state memory is updated; (b) a transmitting apparatus memory such as a request register for storing information indicating a transmitting apparatus which is the second information processing apparatus to transmit the information, a use-channel which is to be used by the transmitting apparatus and an occupy-period which is the transmission occupation period to be occupied by the transmitting apparatus; (c) an insuring device such as a register writer for insuring the use-channel and the occupy-period on the basis of a monitoring result of the monitoring device; and (d) a reporting device such as a command generator for reporting a fact of insuring the use-channel and the occupy-period through the communication bus to the second information processing apparatus when the use-channel and the occupy-period can be insured by the insuring device.
According to the second transmission managing apparatus of the present invention, the transmission managing apparatus insures and reports the use-channel and the occupy-period in place of the transmission processing apparatus. Thus, when the memory content of the transmission state memory is not changed so that the use-channel and the occupy-period cannot be insured, it is possible to prevent a useless operation of trying to insure the use-channel and the occupy-period from being performed by the information processing apparatus. Thus, it is possible for the transmission processing apparatus to insure the use-channel and the occupy-period efficiently.
Therefore, it is possible to prevent the communication bus from being used for the useless referring operation, so that the usage efficiency can be improved as a whole of the information transmitting system. Further, it is possible to prevent the process load from being increased by the useless insuring operation in the information processing apparatus.
The above object of the present invention can be also achieved by a second information processing apparatus included in the above described second information transmitting system of the present invention together with the above described second transmission managing apparatus of the present invention. The second information processing apparatus is provided with: (a) a memory controlling device such as a resource insure request unit for controlling the transmitting apparatus memory to store the use-channel and the occupy-period; and (b) a transmitting device such as a packet transmitter for transmitting the information by using the use-channel and occupying the occupy-period when a fact that the use-channel and the occupy-period can be insured is reported by the reporting device.
According to the second information processing apparatus, when the use-channel and the occupy-period cannot be insured, the operation of trying to insure the use-channel and the occupy-period is not performed. Thus, it is possible to insure the use-channel and the occupy-period efficiently.
Therefore, it is possible to prevent the process load from being increased by the useless insuring operation in the information processing apparatus.
In one aspect of the second information processing apparatus of the present invention, the second information processing apparatus is further provided with: (c) a referring device such as a transmission controller for referring to the memory content when the information is to be transmitted; and (d) a channel and period insuring device such as a transmission controller for insuring the use-channel and the occupy-period on the basis, of the referred memory content, the memory controlling device controlling the transmitting apparatus memory to store the use-channel and the occupy-period only when the use-channel and the occupy-period cannot be insured by the channel and period insuring device.
According to this aspect, only in case that the non-used channel and the preservable period cannot be insured, the transmission managing apparatus performs the insuring operation in place of the information processing apparatus. Thus, it is possible, while restraining the process load of the transmission managing apparatus to the minimum, to perform the insuring operation efficiently.
The above object of the present invention can be also achieved by a second information transmitting system provided with the above described second transmission managing apparatus and a plurality of second information processing apparatuses each having the same construction as the above described second information processing apparatus of the present invention, wherein the information transmission is carried out between the second information processing apparatuses.
According to the second information transmitting system, since each of the information processing apparatuses insures the use-channel and the occupy-period efficiently to thereby transmit the information, it is possible to transmit the information efficiently as a whole of the information transmitting system.